Songwriters and poets have depicted their dislike of barriers. In his only cowboy song, Cole Porter in 1934 proclaimed, “Don’t fence me in … give me land, lots of land.” Robert Frost told us, “Something there is that doesn’t love a wall.” However, both would have been surprised that the issue of the building of a wall would be central and highly controversial in the 2016 presidential election, and perhaps a leading factor in the election of Donald Trump as president.

Political barriers were not unknown in the past. The remains of the Great Wall of China, 2,000 years old and thousands of miles long, is a reminder of this. Nevertheless, they were not common. At the end of World War II in 1945, only five border walls existed in the world. But a funny thing happened on the way to globalization, which logically entails the removal of barriers. The process may have removed some obstacles, but there has been in the last 20 years an increasing dimension in the construction of walls and fences.

The issue thirty years ago was symbolically illustrated in Germany. Speaking on June 12, 1987 at the Brandenburg Gate in West Berlin, a few yards from the Berlin wall, President Ronald Reagan first said, in his only German utterance, “Es gibt nur ein Berlin” (there is only one Berlin). In fact, there were two, since the communist German Democratic Republic had in August 1961 constructed a wall that divided the city and restricted freedom of movement. In his desire to end the Cold War, Reagan then uttered his famous line calling on Soviet general secretary Mikhail Gorbachev to “tear down this wall.” Gorbachev, though a reformer, did not do so, but the combination of popular protest, mass pressure, and decline of the power of the Soviet Union succeeded in forcing it to be opened on November 9, 1989, and to be demolished in the next years.

What is relevant is that when the Berlin Wall fell, there were some 16 border fences around the world. Today, 65 countries have or are building walls to protect themselves for security reasons, to combat the threat of terrorism, or to prevent unwanted migrants entering the country.

Donald Trump as presidential candidate, and now as president, using strong and controversial rhetoric, has made building a wall along the 1,900-mile border with Mexico a crucial issue and a pivotal element of his policy. The rationale is to prevent illegal aliens, criminals, and drugs from entering the United States. It is not yet clear how much that wall will cost – some estimates suggest $21 billion – or who will pay for it (federal funds or reimbursement by Mexico). Whatever the answer, the insistence on border control is fundamental. Trump on January 25, 2017 signed two executive orders for the construction of a contiguous wall along the border, as well as for increasing the number of immigration enforcement officers who carry out deportations.

Interestingly, while a candidate, Trump, defending his call for a wall, often cited Israel’s security barrier that was created to stop terrorism from the West Bank as if it were a model to be copied. Certainly, the Israeli barrier resulted in a dramatic decline in suicide bombers entering Israel. Now, however, Israel is facing terrorists in the Gaza Strip. It is therefore planning to build a large underground wall around Gaza and into the Mediterranean to stop the Hamas terrorists using underground tunnels as they did in the 2014 war, also called Operation Defensive Edge.

The task is urgent and essential. In the 2014 war, Israel destroyed 32 tunnels built by Hamas. That group has greatly expanded its naval commando unit, now consisting of 1,500 frogmen. Not only is Hamas still firing rockets from Gaza, one of which landed near Ashkelon, but the terrorist organization is still, contrary to international law, building tunnels underneath the schools in Gaza. The new Israeli project, a concrete wall, 40 miles long, 20 feet high, and 130 feet deep, using advanced sensor and monitoring devices to detect tunnels, together with an offshore barrier, will be built on Israeli territory, parallel to the border fence.

A wall is urgent and needs no apology. Hamas tunnels still exist, partly to use for smuggling from and to Egypt, partly as command centers and weapons storage, and partly for offensive operations against Israeli civilians. Many of these tunnels run under civilian homes in the Gaza Strip.

Similarly, no apologies are needed for the dramatic increase in walls and barriers in the 21st century. They result from security arrangements for barriers concerned with changing conditions in the world, economic inequality, wars, and above all terrorism, all of which displace people. They are needed in a world of increasing migration, with obvious effects on a country’s budgets, employment, and cultural cohesion.

The U.S. and Israel are not the only advocates for barriers. It is worthwhile to indicate a few of the other 65 walls or barriers. Morocco has a 1,700-mile wall against the West Sahara called “the Berm,” to protect it from Polisario rebels. In 2014, to ensure security at the Spanish Enclaves in North Africa, especially at Melilla, Morocco built a five-yard-high fence with razor wire and blades along the top.

Saudi Arabia has a 560-mile fence against Iraq. Turkey is busy. It has a 90-mile wall against Iran, is planning a barrier against Iraq, and has a 566-mile barrier to prevent ISIS invaders from Syria. Hungary has a 110-mile, 13-foot-high fence against Serbia. There is a 2,500-mile barbed wire fence between India and Pakistan. Since 1974, Cyprus is divided between ethnic Greeks in the south and Turks in the north. The city of Belfast is virtually divided with ironically termed “peace lines” separating Catholics and Protestants.

The final paradox in this story is a new phenomenon, the peaceful revolt in recent years of citizens in European countries against the influx of tourists. In 2017, this has occurred in Spain, which got 75 million visitors in 2016; in Venice, which got 20 million and suffers from large cruise ships and pollution; in Barcelona; and in Dubrovnik. The story now is “welcome stranger, but only up to a point.”

Songwriters and poets have depicted their dislike of barriers. In his only cowboy song, Cole Porter in 1934 proclaimed, “Don’t fence me in … give me land, lots of land.” Robert Frost told us, “Something there is that doesn’t love a wall.” However, both would have been surprised that the issue of the building of a wall would be central and highly controversial in the 2016 presidential election, and perhaps a leading factor in the election of Donald Trump as president.

Political barriers were not unknown in the past. The remains of the Great Wall of China, 2,000 years old and thousands of miles long, is a reminder of this. Nevertheless, they were not common. At the end of World War II in 1945, only five border walls existed in the world. But a funny thing happened on the way to globalization, which logically entails the removal of barriers. The process may have removed some obstacles, but there has been in the last 20 years an increasing dimension in the construction of walls and fences.

The issue thirty years ago was symbolically illustrated in Germany. Speaking on June 12, 1987 at the Brandenburg Gate in West Berlin, a few yards from the Berlin wall, President Ronald Reagan first said, in his only German utterance, “Es gibt nur ein Berlin” (there is only one Berlin). In fact, there were two, since the communist German Democratic Republic had in August 1961 constructed a wall that divided the city and restricted freedom of movement. In his desire to end the Cold War, Reagan then uttered his famous line calling on Soviet general secretary Mikhail Gorbachev to “tear down this wall.” Gorbachev, though a reformer, did not do so, but the combination of popular protest, mass pressure, and decline of the power of the Soviet Union succeeded in forcing it to be opened on November 9, 1989, and to be demolished in the next years.

What is relevant is that when the Berlin Wall fell, there were some 16 border fences around the world. Today, 65 countries have or are building walls to protect themselves for security reasons, to combat the threat of terrorism, or to prevent unwanted migrants entering the country.

Donald Trump as presidential candidate, and now as president, using strong and controversial rhetoric, has made building a wall along the 1,900-mile border with Mexico a crucial issue and a pivotal element of his policy. The rationale is to prevent illegal aliens, criminals, and drugs from entering the United States. It is not yet clear how much that wall will cost – some estimates suggest $21 billion – or who will pay for it (federal funds or reimbursement by Mexico). Whatever the answer, the insistence on border control is fundamental. Trump on January 25, 2017 signed two executive orders for the construction of a contiguous wall along the border, as well as for increasing the number of immigration enforcement officers who carry out deportations.

Interestingly, while a candidate, Trump, defending his call for a wall, often cited Israel’s security barrier that was created to stop terrorism from the West Bank as if it were a model to be copied. Certainly, the Israeli barrier resulted in a dramatic decline in suicide bombers entering Israel. Now, however, Israel is facing terrorists in the Gaza Strip. It is therefore planning to build a large underground wall around Gaza and into the Mediterranean to stop the Hamas terrorists using underground tunnels as they did in the 2014 war, also called Operation Defensive Edge.

The task is urgent and essential. In the 2014 war, Israel destroyed 32 tunnels built by Hamas. That group has greatly expanded its naval commando unit, now consisting of 1,500 frogmen. Not only is Hamas still firing rockets from Gaza, one of which landed near Ashkelon, but the terrorist organization is still, contrary to international law, building tunnels underneath the schools in Gaza. The new Israeli project, a concrete wall, 40 miles long, 20 feet high, and 130 feet deep, using advanced sensor and monitoring devices to detect tunnels, together with an offshore barrier, will be built on Israeli territory, parallel to the border fence.

A wall is urgent and needs no apology. Hamas tunnels still exist, partly to use for smuggling from and to Egypt, partly as command centers and weapons storage, and partly for offensive operations against Israeli civilians. Many of these tunnels run under civilian homes in the Gaza Strip.

Similarly, no apologies are needed for the dramatic increase in walls and barriers in the 21st century. They result from security arrangements for barriers concerned with changing conditions in the world, economic inequality, wars, and above all terrorism, all of which displace people. They are needed in a world of increasing migration, with obvious effects on a country’s budgets, employment, and cultural cohesion.

The U.S. and Israel are not the only advocates for barriers. It is worthwhile to indicate a few of the other 65 walls or barriers. Morocco has a 1,700-mile wall against the West Sahara called “the Berm,” to protect it from Polisario rebels. In 2014, to ensure security at the Spanish Enclaves in North Africa, especially at Melilla, Morocco built a five-yard-high fence with razor wire and blades along the top.

Saudi Arabia has a 560-mile fence against Iraq. Turkey is busy. It has a 90-mile wall against Iran, is planning a barrier against Iraq, and has a 566-mile barrier to prevent ISIS invaders from Syria. Hungary has a 110-mile, 13-foot-high fence against Serbia. There is a 2,500-mile barbed wire fence between India and Pakistan. Since 1974, Cyprus is divided between ethnic Greeks in the south and Turks in the north. The city of Belfast is virtually divided with ironically termed “peace lines” separating Catholics and Protestants.

The final paradox in this story is a new phenomenon, the peaceful revolt in recent years of citizens in European countries against the influx of tourists. In 2017, this has occurred in Spain, which got 75 million visitors in 2016; in Venice, which got 20 million and suffers from large cruise ships and pollution; in Barcelona; and in Dubrovnik. The story now is “welcome stranger, but only up to a point.”